Bumble bee queens initiate nests solitarily and transition to living socially once they successfully rear their first cohort of offspring. Bumble bees are disproportionately important for early season pollination, and many populations are experiencing dramatic declines. In this system, the onset of the social stage is critical for nest survival, yet the mechanisms that facilitate this transition remain understudied. Further, the majority of conservation efforts target the social stage of the bumble bee life cycle and do not address the solitary founding stage. We experimentally manipulated the timing of worker emergence in young nests of bumble bee (Bombus impatiens) queens to determine whether and how queen fecundity and survival are impacted by the emergence of workers in the nest. We found that queens with workers added to the nest exhibit increased ovary activation, accelerated egg laying, elevated juvenile hormone (JH) titres and also lower mortality relative to solitary queens. We also show that JH is more strongly impacted by the social environment than associated with queen reproductive state, suggesting that this key regulator of insect reproduction has expanded its function in bumble bees to also influence social organization. We further demonstrate that these effects are independent of queen social history, suggesting that this underlying mechanism promoting queen fecundity is reversible and short lived. Synchronization between queen reproductive status and emergence of workers in the nest may ultimately increase the likelihood of early nesting success in social systems with solitary nest founding. Given that bumble bee workers regulate queen physiology as we have demonstrated, the timing of early worker emergence in the nest likely impacts queen fitness, colony developmental trajectories and ultimately nesting success. Collectively, our findings underline the importance of conservation interventions for bumble bees that support the early nesting period and facilitate the production and maintenance of workers in young nests.

中文翻译：

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大黄蜂生活史的一个组织特征：工蜂的出现促进了蜂王在幼巢中的繁殖和生存

大黄蜂蜂王独自筑巢，一旦成功养育了第一批后代，就会过渡到社交生活。大黄蜂对于早期授粉非常重要，许多种群正在经历急剧下降。在这个系统中，社会阶段的开始对于巢穴的生存至关重要，但促进这种转变的机制仍未得到充分研究。此外，大多数保护工作都针对大黄蜂生命周期的社会阶段，而不是针对单独的创始阶段。我们通过实验操纵了大黄蜂 (Bombus impatiens) 蜂后幼巢中工蜂出现的时间，以确定蜂巢中工蜂的出现是否以及如何影响蜂王的繁殖力和生存。我们发现，巢中添加工人的蜂后表现出卵巢激活增加、产卵加速、保幼激素 (JH) 滴度升高，并且相对于单独的蜂后死亡率也较低。我们还表明，JH 受社会环境的影响比与蜂王生殖状态相关的影响更大，这表明这种昆虫繁殖的关键调节剂已经扩大了其在大黄蜂中的功能，也影响了社会组织。我们进一步证明了这些影响与女王的社会历史无关，这表明这种促进女王繁殖力的潜在机制是可逆的并且是短暂的。蜂王繁殖状态与巢中工人出现之间的同步可能最终会增加在单独巢穴建立的社会系统中早期筑巢成功的可能性。正如我们已经证明的那样，鉴于大黄蜂工蜂调节蜂王的生理机能，蜂巢中早期工蜂出现的时间可能会影响蜂王的健康状况、蜂群发育轨迹以及最终的筑巢成功率。总的来说，我们的研究结果强调了大黄蜂保护干预措施的重要性，这些干预措施支持早期筑巢期并促进幼巢中工人的生产和维护。